Journal of Materials in Civil Engineering

Hydraulic structures play an important role in regulation and transport of water in reservoirs and open channels. Examples of such structures include concrete spillways, stilling basins, flumes, weirs, dam, and culverts. Under the impact of water flow, the concrete surfaces suffer inevitably from abrasive erosion. Most existing standards for abrasion determine mass loss or discrete depth measurements. In this study, 3D laser scanning technology was used to determine abraded volume loss and surface topography in addition to mass loss. Surface scans were analyzed using commercial software. Assuming standard concrete density, it was generally found that mass measurements were higher than expected when compared with the calculated volume measurements, but the ranking of resistance is the same for both techniques. The scanning technology presents an alternative method to measure abrasion.

The issue of steel bar corrosion has seriously affected the working performance of concrete structures. Reinforcement is an effective measure to restore the mechanical properties and prolong the service life of concrete structures. Determining the bond properties between textile-reinforced concrete (TRC)–confined concrete and a corroded steel bar is one of the main issues in evaluating the effect of TRC reinforcement. Based on the results of electrochemical corrosion and pullout tests, the bond properties between concrete and a steel bar under unconfined and TRC–confined conditions were comparatively analyzed in terms of the corrosion-induced cracking, failure mode, bond-slip curve, bond strength, and bond failure mechanism. The empirical calculation formula of the ultimate bond strength between unconfined concrete and a corroded steel bar was obtained, and the confinement effects of TRC and fiber-reinforced polymer (FRP) were compared by collecting data from the relevant literature. The research results indicated that TRC confinement can effectively improve the bond properties between concrete and a corroded steel bar and limit the development of corrosion-induced cracks. Furthermore, TRC confinement controlled any further crack expansion during the pulling out of the steel bar. After TRC confinement, the brittle failure characteristic of the bond behavior between concrete and a corroded steel bar was improved, and the failure mode was changed from splitting to splitting–pullout. The confinement effect of TRC using a lower fiber-reinforcement ratio is similar to that of FRP.

The present study proposed an adhesion model that incorporates effects of a warming asphalt agent, asphalt, and aggregate in a nonwater or water environment according to the surface free energy theory. The results indicated that the water stability of the recycled asphalt mixture could be evaluated by the adhesion work ratio under water or nonwater conditions. The polar component of the asphalt and the Lewis acid-base force parameter were changed by adding the warming agent; accordingly, the surface free energy of the asphalt was improved, the adhesion ability of the asphalt and the stone was enhanced, and the water stability of the recycled asphalt mixture was promoted.

Stainless steel has broad application prospects in building structures because of its favorable corrosion resistance and durability, attractive appearance, and easy conformity with architectural aesthetics. In order to evaluate in-fire and postfire structural behavior of stainless-steel structures, the in-fire and postfire mechanical properties of duplex stainless steel S22053, including elasticity modulus, nominal yield strength, ultimate strength, elongation after fracture, and microstructure, were obtained by 111 standard tests. Among them, the in-fire tests considered the effect of exposure temperature (ranging from 20°C to 700°C) on mechanical properties, and the postfire tests considered the effects of exposure temperature (20°C, 200°C, 400°C, 600°C, 800°C, and 1,000°C), high-temperature exposure duration (0.5, 3, 10, and 20 h), and cooling mode (air cooling and water cooling). Also, the test results were compared with ordinary carbon steel, high-strength structural steel, austenitic stainless steel, ferritic stainless steel, and European standards; and the characteristics of mechanical properties of S22053 are summarized. Predictive equations of the mechanical properties of in-fire and postfire S22053 are established by fitting to the test data with the least-squares method. The predicted results using the established equations are highly consistent with the experimental data. Thus, the equations can provide key data for residual mechanical property evaluation of stainless-steel structures.

It is widely known that presoaked lightweight aggregate (LWA) is greatly beneficial for reducing autogenous shrinkage by providing additional water reservoirs for the mixture. However, in unsealed conditions, when concrete is subjected to drying, addition of LWA to the mixture might not be as effective in reducing drying shrinkage. This study examines the effects of LWA addition on drying shrinkage in different boundary conditions. By varying the number of sides exposed to the surrounding unsaturated environment, the severity of drying condition is altered, and its effect on drying shrinkage of mixes with LWA is studied. The performance of LWA in reducing drying shrinkage of mortar samples is shown to be highly dependent upon the exposure condition and the extent of external curing. The results of this work indicate that curing concrete internally may be an inadequate shrinkage-compensating strategy in a severe drying condition and when no external curing is implemented. Nonetheless, mixtures with LWA exhibited a denser microstructure which can be advantageous in terms of durability.

Natural fibers are environment-friendly and efficient for soil reinforcement. Many studies have reported the influences of fiber percentage on the shear strength of fiber reinforced soil. However, different natural fibers perform differently in the soil reinforcement because of their different physical and chemical properties. In this study, the physical and chemical properties of natural fibers (i.e., natural moisture content, specific gravity, breaking tensile strength, breaking strain, cellulose, hemicellulose, lignin, and ash) were examined for their influences in the soil reinforcement. Experimental data of unconfined compressive strength (UCS) for three types of natural fibers (coir, jute, and water hyacinth) were collected from the literature. A total of 11 factors including soil moisture content, soil density, and fiber percentage were evaluated by using the Bayesian nonparametric general regression (BNGR) method. The robustness of the BNGR algorithm was validated using $k$-fold cross-validation. A parametric study was carried out to unveil the effects of these input variables. The results indicated that a higher fiber percentage or larger soil density induces higher reinforcement effect. Besides, the cellulose in a natural fiber is found to have a significant effect on the UCS, followed by the ash, whereas the other chemical components, i.e., hemicellulose and lignin, have less association with soil reinforcement. With respect to the physical properties, the breaking strain is found to be highly correlated with the UCS, whereas the effects of fiber natural moisture content, specific gravity, and breaking tensile strength are less significant parameters.

This paper summarizes the results of a research study that used microscale and macroscale tests to examine the effects of reclaimed asphalt pavement (RAP) source and RAP percentage on the cracking resistance of asphalt mixes with high RAP content. Atomic force microscopy (AFM) was used to study the microstructure and the adhesion properties of binders of two different RAP sources. In addition, asphalt mixes with three RAP percentages were designed using the two RAP materials considered. The low-temperature cracking resistance and fatigue cracking resistance of the designed mixes were evaluated. The results of the AFM experiments indicated that the microstructure of the RAP binders was different from that of the virgin asphalt binders. While the adhesive properties of RAP binders were statistically different from each other, both RAP binders had significantly lower adhesion than the virgin asphalt binders used. The results of macroscale tests indicated that the RAP source has a significant effect on the fatigue cracking resistance of RAP asphalt mixes, particularly those with more than 30% RAP. This might be attributed to differences in the adhesive properties of the RAP binders. Therefore, it is very important to determine the adhesive properties of the RAP binders. The results also indicated that using a virgin asphalt binder with appropriate low-temperature performance grade can help ensure satisfactory low-temperature cracking resistance of mixes with up to 50% RAP.

A fracture mechanics–based approach is developed to predict the shrinkage cracking age of shotcrete ring specimens under various curing regimes. Prolonged water curing and curing compound are considered to mitigate early-age shrinkage cracking. The maximum allowable tensile strain is determined based on a fracture criterion using R- and G-curves. The actual tensile strain of rings calculated from the measured free shrinkage and estimated creep is then used to predict the shrinkage cracking age by comparing the maximum allowable tensile strain. The determined maximum allowable tensile strain slightly increases as the age of a beam increases. Prolonged water curing has significant benefits on the mitigation of shrinkage cracking of shotcrete, and a lower increasing rate of actual tensile strain is observed. Specimens with curing compound show excellent shrinkage cracking mitigation, and cracks are never triggered owing to low shrinkage and creep. The theoretical predicted cracking ages exhibit a good correlation with measured ones. This proposed model is found to be capable of effectively and accurately predicting cracking tendency of ring specimens exposed to drying environments.

The impact of hot-mix asphalt (HMA) density differentials on thermal streaks and their temporal evolution were examined by means of infrared thermography under laboratory conditions. A series of experimental tests was performed using specimens containing three asphalt blocks, one of which had an arbitrarily lower density and was positioned between the other two blocks with higher densities. The specimens were uniformly heated to a temperature similar to that found in real on-site situations during HMA laydown and left to cool at ambient temperature, simulating a thermal streak caused by density differentials. Surface cooling at ambient temperature was recorded using a thermographic camera. Results demonstrated that HMA density variations of 6.5% or higher produce surface temperature differentials of 4°C or more after 3 min of cooling, and can be straightforwardly detected by infrared thermography. Thermal modeling confirmed the experimental trends and constitutes a valuable tool for future investigation under different conditions.

In this paper, experiments of recycled aggregate concrete under multiaxial compression with five different replacement ratios (0%, 25%, 50%, 75%, and 100%) of coarse aggregates were implemented by using the true triaxial apparatus and the failure modes were compared under different conditions. According to the obtained stress-strain curves, the peak stresses and peak strains were extracted and analyzed to study the mechanical properties of recycled aggregate concrete under multiaxial compression. Meanwhile, the failure modes are described. The results show that the increasing coefficients of peak stresses of recycled aggregate concrete under biaxial compression are higher than those of ordinary concrete, with the highest pertaining to the replacement ratio of 75%. Nevertheless, the increasing coefficients of peak stresses of recycled aggregate concrete under triaxial compression are lower than those of ordinary concrete. As for peak strains analysis, those under uniaxial compression exceed those under biaxial compression, which are lower than those under triaxial compression. The peak strains of ordinary concrete are higher than those of recycled aggregate concrete, with that of 100% replacement ratios being the lowest. Based on the experimental data and the failure characteristics, the failure criteria of recycled aggregate concrete with different replacement ratios under multiaxial compression are proposed, which is of great significance to the research and application of secondary utilization of concrete waste as well as building environmental protection.

With the aging of tunnel structures, rehabilitation and repair has become an increasingly important part of tunnel maintenance. This paper investigates the use of alkali-activated mortar for tunnel-lining structure repair. First, the effects of NaOH concentration and ordinary portland cement (OPC) content on the fresh and hardened states of alkali-activated repair mortar (ARM) were studied by investigating its setting time and compressive strength. Second, the bond strength of ARM made from the optimum mix proportion was compared with that of cement repair mortar (CRM) using a self-design tunnel-lining-crack-treatment platform (TLCTP). Finally, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were undertaken to study the morphology, mineral composition, and hydration products of ARM and CRM. It is found that the setting times of ARM are greatly shortened and its compressive strength is noticeably increased with increasing OPC content. Increasing the NaOH concentration from 10 to 12 M induces decrease in setting times and increase in compressive strength of ARM, but further increasing NaOH concentration to 14 M results in a slight increase in setting times and decrease in the compressive strength of ARM. Bond strength test results show that ARM made from an optimum mix proportion exhibits a bond strength superior to that of CRM in dry curing conditions. Although the presence of water has a negative effect on bond strength, ARM still shows better bond strength than CRM. XRD characterization indicates that ARM consists of sodium aluminosilicate hydrate (NASH) gel and calcium silicate hydrate (CSH) gel that are responsible for increasing its strength. SEM characterization reveals that ARM has a dense structure with voids filled with cementing agents, whereas the CRM shows a rough structure with small cracks and unfilled pores. The dense microstructure benefits the reduction in crack propagation and water absorption, leading to high compressive and bond strengths.

Every year millions of bottles of polyethylene terephthalate (PET) are discarded into the environment, when in fact these materials have a high potential to be recycled and/or beneficially reused. This study aims to evaluate the mechanical behavior of a clayey soil mixed with 10%, 20%, and 30% of fine crushed PET and with 3% and 5% of PET flakes. These new materials can possibly be used in myriad applications in geotechnical engineering. Triaxial tests at 50, 150, and 300 kPa confining stresses were performed to obtain the strength parameters of the soil-PET mixtures. The results show that, overall, the strength improvements of the mixtures were considerable; the friction angle had a substantial enhancement, while the cohesion slightly decreased with the addition of the PET. The soil strength parameters were highly influenced by the percentage of fine crushed PET and PET flakes added to the mixture. Improvements also depended on the confining level to which the samples were submitted. This new geotechnical material can be used in landfills, as well as for slopes stabilization and other geotechnical works, contributing to a better understanding and interpretation of the behavior of soil reinforced with PET material and giving an environmentally friendly end to this residue.

This study aims to evaluate the influence of the addition of coarse recycled concrete aggregate (CRCA) on the rutting and stiffness of Ontario Superpave mixtures. Mix designs of asphalt mixtures were performed for two types of CRCA at various proportions. To enhance the properties of CRCA, a combination of different treatment methods was investigated. The physical characteristics of treated and untreated CRCA were evaluated. The impact of treated and untreated CRCA on the rutting resistance of asphalt mixtures was determined. The obtained results indicated that the use of a combination technique of different treatment methods is a highly successful method for improving various physical properties. The addition of two types of untreated CRCA in various proportions produces higher rutting resistance and higher stiffness than the control mix. The CRCA type has an effect on the rutting characteristics of asphalt mixtures. The application of treated CRCA with heat treatment and short mechanical treatment leads to an increase in the rutting resistance, a decrease in the total rut depth, a slight increase in the stiffness, and an increase in the rutting parameter of asphalt mixtures depending on the type of CRCA. The application of treated CRCA with a presoaking method and short mechanical treatment results in an increase in the stiffness and rutting factor of mixtures depending on the type of CRCA. The results indicate that the application of different CRCA types in various forms—treated and untreated—is very successful and can contribute significantly toward more RCA applications with asphalt pavements.

In this research the constitutive behavior of high-performance fiber-reinforced cementitious composites (HPFRCCs) was evaluated experimentally under uniaxial monotonic tension and cyclic loading. The experimental program included 10 different mixtures manufactured using two fiber types, including polyvinyl alcohol (PVA) fibers and twisted steel fibers, with ratios of 1%, 2%, and 3% by volume of the mixture. Mixtures were manufactured containing one fiber type, referred to here as a mono mixture, or containing both fiber types, a hybrid mixture. A testing jig and a testing procedure were developed to evaluate the response of HPFRCCs under monotonic tension loading, cyclic tension-only loading, and cyclic tension-compression loading. The testing results provide benchmark cyclic constitutive curves for mono and hybrid HPFRCC mixtures. In addition, the testing results indicate that the hybrid mixtures achieved an overall improved performance compared to the mono mixtures. On average, hybrid mixtures achieved better performance compared to PVA and steel mono mixtures by achieving higher toughness, higher energy absorption capacity during hardening, higher energy absorption capacity during softening and moderate toughness reduction during cyclic loading.

This research presents results from experimental studies of the mechanical behavior of steel bolts of Grade 8.8 and 10.9 after experiencing fire conditions. A significant number of steel bolts of Grade 8.8 and 10.9 of different sizes were heated according to a specific time-temperature curve and then cooled. By performing various experiments on these samples, mechanical properties of steel bolts such as stress-strain curves, elasticity modulus, ultimate strengths and the yield limit strengths of the bolts after the fire were obtained. Results from the experiments showed a quick reduction in the residual strength of the bolts when heated to temperatures of 500°C for both grades. Based on the large number of experiment results, two sets of equations for determining the mechanical properties of steel bolts of Grade 8.8 and 10.9 were presented.

Epoxy asphalt mixture has been widely used as an excellent paving material on long-span steel bridges; however, low-temperature cracking is a significant concern for paving on an orthotropic steel deck. Analysis of low-temperature thermal stress can be a challenge owing to the varying modulus of epoxy resin asphalt mixture at different temperatures. This paper presents an investigation into the rheological behaviors and models for epoxy resin asphalt mixture under different temperatures. Bending creep tests were conducted in a range of temperatures from 10°C to 60°C, and creep compliance curves were obtained. Based on the test results, five succinct but practical viscoelastic models were used for creep modeling, and parameters corresponding to different temperatures were obtained. Using a numerical approach, the creep compliance results were converted into master curves of relaxation modulus, and then the low-temperature thermal stress was calculated for the pavement layer. The experimental and simulation results indicated that the modified second-order extensive Kelvin model could be used to describe creep performance very well for epoxy resin asphalt mixture in a wide range of temperatures, and epoxy asphalt is highly adaptable to a cold working environment when used as the paving layer of steel bridge decks.

This paper investigates the performance of steel fiber–reinforced alkali-activated slag concrete incorporating different fly ash replacement percentages. Three different molarities of sodium hydroxide (SH) were combined with sodium silicate to activate the binding phase. Double hooked-end steel fibers were incorporated into the alkali-activated mix in varying volumetric proportions up to 3% to enhance its ductility. Blended binder, alkali-activator solution, dune sand, and coarse aggregate contents were proportioned and samples were cured at ambient conditions. Results showed that higher slag content, molarity of SH, and fiber addition led to less-workable concretes but with improved mechanical properties, especially at early ages. Fly ash replacement of 25% could enhance mechanical performance after 28 days. Analytical models correlating mechanical properties were developed for alkali-activated slag concretes with fly ash. Scanning electron microscopy, differential scanning calorimetry, and Fourier transform infrared spectroscopy highlighted the coexistence of calcium aluminosilicate hydrate and sodium aluminosilicate hydrate gels.

Mine tailings cause significant storage and environmental problems because a large amount of tailings containing potentially numerous hazardous contaminants is generated during mining operations. Therefore, the utilization of mine tailings in different sectors should be taken into consideration to minimize the storage efforts and environmental pollution problems. In this two-stage study, the alkali activation opportunity of waste clay containing boron (WCB) discarded from boron mine production was investigated. In the first stage of this study, alkali activation of WCB calcined at different temperatures between 500°C and 800°C was investigated under steam-curing conditions. It was found that a calcination temperature of at least 700°C is necessary to initiate the alkali activation of WCB, whereas the maximum compressive strength value was obtained at 800°C. Subsequently, the effects of alkaline activator solution type (sodium hydroxide and sodium silicate) and quantity on the development of engineering properties of alkali-activated WCB mortars, such as compressive and flexural strength, water sorptivity, and drying shrinkage, were investigated by using WCB calcined at 800°C. Furthermore, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA/DTA), and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analyses were carried out on the hardened paste mixtures. The minimum activator concentration for alkali activation of calcined WCB was 6% ${\mathrm{Na}}_2\mathrm{O}$ by weight of WCB with a minimum silicate modulus ($M_s={\mathrm{SiO}}_2/{\mathrm{Na}}_2\mathrm{O}$) of 1.2. A compressive strength value up to 38 MPa along with acceptable water absorption characteristics and drying shrinkage values can be obtained from alkali activation of calcined WCB at 800°C. NaOH activator was not as effective as sodium silicate activator in activating WCB, even in high dosages.

Conventional portland cement–based aerated concrete needs autoclaved curing in order to obtain high early-stage strength. Magnesium phosphate cement–based lightweight materials, such as aerated magnesium phosphate cement and magnesium phosphate cement–based foamed concrete can achieve the high early strength without thermal curing. In this study, metakaolin was introduced to enhance the performance of aerated magnesium phosphate cement, and the compressive strength, splitting tensile strength, thermal conductivity, foamability, strength retention coefficient after water immersion, sorptivity, and hygroscopicity were measured. Experimental results indicate that the presence of metakaolin has a slight influence on thermal insulation performance, and its strength and water resistance were improved significantly. The 3-h compressive strength of metakaolin-blended aerated magnesium phosphate cement can reach approximately 3 MPa. Metakaolin slightly slows down the gas-foaming process, and a larger amount of finer pores and smaller amount of capillary interconnected pores are produced. For this reason, the height of water migration in aerated magnesium phosphate cement with metakaolin is lower than that without metakaolin. Likewise, metakaolin decreases the hygroscopic moisture content of aerated magnesium phosphate cement, and the hygroscopicity, which can be described by several classical sorption isotherm models, reveals the typical characteristics of the hygroscopic property of portland cement–based porous materials.

While aggregates are predominantly responsible for concrete properties, influences of coarse-aggregate shapes (form and angularity) and surface texture on concrete mechanical performance are not well understood. This paper designed and tested a series of concrete specimens manufactured with coarse aggregates varied in form, angularities, and surface textures, which enabled us to systematically analyze the influence of these features on the overall mechanical performance of concrete materials. The coarse aggregates form, angularity, and surface texture were quantified by the flat and elongated ratio (FER), angularity index (AI), and surface roughness (SR), respectively. Test results indicated that the splitting tensile strength and compressive strength of concrete were enhanced with an increased SR but dropped significantly with an increase in the FER or AI. Both of the elastic modulus and Poisson’s ratio decreased slightly with the increase in FER or AI, yet increased with an increase in SR. A mesomechanical model was introduced to estimate the performance of materials with results validated by those obtained from the test. The effects of the random FER, AI, and SR on the variability of concrete mechanical properties were further simulated in-depth. All research results confirmed that random FER, AI, and SR of coarse aggregates have considerable effects on the variability of concrete mechanical properties.

Calcium carbonate–based biominerals are considered self-healing materials in concrete. The morphology and mineralogy of biominerals depend highly on the self-healing efficiency of concrete cracks. This study examined the morphology and mineralogy of biominerals with a new isolate, Bacillus sp. BY1, and various organic calcium compounds (i.e., calcium formate, calcium acetate, and calcium lactate). In addition, compressive strength and crack self-healing efficiency were investigated under various other conditions. Biominerals formed in the presence of calcium formate and calcium lactate were mostly calcite (ca. 95% by weight) and contained more rhombohedral faces, whereas calcium acetate induced spherulite-shaped biominerals with a smaller fraction of calcite (ca. 61.5% by weight). With the addition of bacteria and organic calcium compounds, the compressive strengths decreased and increased, respectively; however, the loss of strength by the bacteria was compensated when both bacteria and organic calcium compounds were added together. Self-healing of cracks did not occur by the addition of bacteria alone and was more prominent when calcium lactate was used as a biomineral precursor.

Rammed-earth (RE) structures are becoming popular because of their sustainability, environment-friendly, and economic advantages. Various studies have investigated the mechanical behavior and energy performance of rammed-earth materials. However, little is known about their fracture behavior. In this study, the fracture properties of RE materials containing different percentages of various stabilizers were investigated using a modified wedge splitting test (WST). The stabilizers were cement, pozzolan, microsilica, glass fiber, guar gum, and phase change material (PCM). Additionally, the effects of these stabilizers on microstructure and phase composition were analyzed using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD), respectively. The results indicated that cement and pozzolan, depending on the pozzolanic reaction, increased the strength of the microstructure while glass fibers led to internal confinement and high ductility that increased the fracture energy of RE materials. However, the phase change material and guar gum reduced the strength and fracture energy of the RE materials. Finally, a statistically significant correlation was obtained between specific fracture energy and other mechanical properties, pointing the way to proper approaches to improve crack resistance of rammed-earth materials.

A simple method for developing a superhydrophobic (SH) asphalt binder surface was developed and examined. This was achieved by thermally fusing micronized tire rubber (MTR) particles on to the asphalt binder surface. Two MTR particle size ranges were prepared, dispersed on the asphalt binder surface, and then cured for durations of 25, 45, and 70 min to investigate the effect of curing time on the contact angle (CA) of MTR–asphalt surface. Sessile drop method was used for CA measurement. Surface profile and morphology of MTR–asphalt interaction were studied and characterized using optical profilometer and scanning electron microscope, respectively. All prepared MTR–asphalt surfaces exhibited an increased CA with a minimum of 36% improvement as compared to the reference. MTR with a higher percentage of smaller particle size cured for 25 min demonstrated the maximum improvement of 42%. In general, the MTR particles transformed the asphalt binder surface by inducing subsurface and surface stresses through embedding and surface bonding to the asphalt, respectively. Effectively stretching the asphalt and altering its surface texture to radially stretched and fine asphalt surface. The intrinsic hydrophobic property of MTR and its induced modification of the asphalt surface can be associated with the improved hydrophobicity of the develop MTR–asphalt surface.

This study evaluated the effectiveness of sludge ash of wood and paper (SAWP) mills for improving the physical and mechanical properties of three different clayey soils. The influence of SAWP was assessed through compaction, Atterberg limits, soaked and unsoaked unconfined compressive strength (UCS), and pulse velocity of compression waves ($Vp$) tests. In addition, changes in the mineralogical and microstructural features of the SAWP-treated samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Finally, toxicity characteristic leaching procedure (TCLP) tests were conducted on the SAWP-treated samples to determine the leachability of heavy metals. Experimental results revealed that SAWP treatment improved physical and mechanical characteristics of all three types of clayey soils. The improvements indicated a considerable decrease in plasticity index and a significant increase in UCS and $Vp$ values. The results of XRD and SEM analyses showed significant changes in the mineralogy and microstructural of the SAWP-treated samples. The changes were attributed to the formation of new cementitious compounds that not only strengthen the bond of particles but also fill the pores resulting in a denser matrix in the SAWP-treated samples. Concentration of leached heavy metals in SAWP-treated samples was less than the permissible values determined by the relevant organizations. The results of this study corroborate the effectiveness of SAWP as a nontraditional additive for soil treatment.

This study investigated the use of glass aggregates as a building and construction material through the assessment of strength, durability, and thermal properties of cement mortars. A combination of crushed glass and glass beads was incorporated in the mortar specimens as 30%, 50%, 70%, and 100% replacement of natural sand. Compressive strength was studied, until 365 days, using standard (20°C) and accelerated (50°C) curing conditions. A decrease in strength was observed with increasing glass aggregate amount. Nonetheless, higher strength gain was evident in glass aggregate mortars cured in standard conditions at later ages. Qualitative analysis of durability by means of plastic shrinkage cracking indicated that full replacement of natural sand with glass aggregates reduces 96% of cracks as compared to mortar containing no glass. Further, chloride permeation of glass aggregate mortars was improved with increasing glass replacement and age due to the inherently impermeable nature of glass particles. Glass aggregates also improved the overall thermal conductivity of mortar because glass itself has low thermal conductivity.

Engineered wood products including wood–plastic composites have been manufactured with different mix designs and different manufacturing techniques within the last years. However, there are still some materials that are not used to manufacture such composites, like recycled high-density polyethylene and camphor wood, although they are available in good quantities as industrial by-products. In this research, wood–plastic composite (WPC) panels were manufactured from high-density polyethylene (HDPE) plastic waste at 20%, 25%, 30%, 35%, and 40% of total weight together with camphor wood waste. Physical, mechanical, and structural properties of the panels were studied and compared according to current standards. The results showed that the properties of the manufactured engineered wood product were significantly affected by the kind and percentage of the wood fiber and plastic waste. Ultimate values of the bending strength of the WPC panels as well as the maximum values of Young’s modulus were reached at 40% plastic content. The water absorption of the panels was found to be inversely related to the HDPE content. The bending strength of the panels with recycled HDPE was less than in the case of using virgin HDPE. The water uptake for WPC panels when using recycled HDPE was higher than the water uptake when using virgin HDPE. Furthermore, the compressive strength of the samples was directly related to its plastic content; it was comparatively low for recycled HDPE panels compared to panels using virgin HDPE.

Results of optimization of an alternative alkali-activated binder (AAB) system based on two industrial waste products found in abundance in Australia, namely fly ash (FA) and granulated blast furnace slag (S), are presented. Early strength development of low-calcium alkali-activated precursors has typically been found to be insufficient for field applications or highly dependent on impractical curing conditions. S can be used effectively to initiate FA bond development without requiring high-temperature curing conditions. The AAB presented was found to exhibit comparable 7- and 28-day strength to cement treated samples, in addition to providing a reduction in vertical shrinkage. AAB exhibited a strong sensitivity to the total water content in the mix; however, acceptable unconfined strengths were achieved for samples with water contents up to 40%. High application rates ($p$ = percentage of dry precursor to total mixture weight) exhibited optimum strength at close to the optimum water content of the sand, whereas lower application rates ($p\le 8–12\%w.t$) were found to show better mechanical strength on the dry side of the optimum water content of the sand. Alkali-activated blends of FA and S, particularly at a $\mathrm{S}:\mathrm{FA}$ ratio of $50:50$, can provide a viable alternative to cement-based binders for the stabilization of granular soils in deep soil mixing projects.

The test method of ASTM C512 (ASTM. 2015. Standard test method for creep of concrete in compression. ASTM C512/C512M. West Conshohocken, PA: ASTM) dictates the use of a spring-loaded creep frame to perform a creep test on concrete. The main thesis of the study is that tests performed using these spring-loaded frames is not a creep test in the sense that the force acting on the specimen is not held constant while the specimen undergoes time-dependent strain. Analysis of this frame is performed using a linear viscoelastic model to represent concrete and isotropic Hooke’s law to represent the steel rods and springs. The internal force and displacement in concrete and steel rods at any given instant of time is found using equilibrium equations and compatibility conditions. It is observed that the force transmitted to the concrete does not remain constant throughout the test duration but is a function of the spring and rod stiffness and the viscoelastic properties of the concrete. Hence, a drop in the magnitude of the force transmitted to the concrete specimen occurs in experiments when a spring-loaded creep frame is used. Experimental validation is also carried out by comparing the response of a spring-loaded creep frame with theoretical results. In this work, optimal spring and rod stiffness values to minimize the drop in the force transmitted to the concrete specimen are established. Thus, this study could be used to determine the linear viscoelastic properties of concrete in a creep frame.

Research intends to improve the durability of asphalt binder and its performance related to rutting and fatigue life. Nanotechnology has been used in many sectors over the years, such as the chemical industry, automotive industry, medicine, and civil engineering. Asphalt binder modification with nanomaterials can improve rutting resistance and alleviate fatigue cracking of asphalt mixtures. In this study, titanium dioxide (${\mathrm{TiO}}_2$) nanoparticles were mixed in a base asphalt binder of penetration grade 50/70 at rates of 0%, 3%, 4%, and 5% by weight of binder. The rheology of the blends was then studied through performance grade (PG), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), penetration test, softening point, and rotational viscosity. The results show that the addition of nanoparticles of titanium dioxide increases the fatigue life and resistance to permanent deformations and to the aging process.

The common laboratory tests for determining the tensile strength of soils can be categorized into direct and indirect methods. For direct methods, there are no standard testing apparatuses or procedures to measure the tensile strength of soils. This paper presents a modification of a direct tension apparatus and its test results on compacted soil. The major factors affecting tensile strength measurements include the size of the specimen, tensile displacement pulling rate, and the shape of the tensile apparatus mold. The effect of the tensile displacement pulling rate and the behavior of crack propagation due to the shapes of the direct tension mold were investigated. Three wedge types (triangular, trapezoidal, and rectangular) were used in the tests. Particle image velocimetry (PIV) technique was adopted to capture the crack propagation along with the development of tensile stress and to evaluate the wedges suitability. In addition, tests were conducted to measure the tensile strength of soils with different specimen depths and cross-sectional areas. The results show that there was no significant influence of the displacement rate associated with tensile force, crack propagation, and maximum tensile force. Triangular wedges are the best pick for direct tension tests. Tensile strength was found to be size dependent; the cross-sectional area and specimen depth govern the tensile strength of compacted soil mixture. However, it was found that the tensile strength was close to a constant when the area ratio exceeds a critical value.

A new type of material, magnesium oxysulfate cement (MOSC), has attracted widespread attention as an environmentally friendly and low-energy inorganic green cementitious material due to its outstanding performance. In this study, electrochemical impedance spectroscopy (EIS) and in situ X-ray diffraction (XRD) were used to characterize the hydration behavior and process of MOSC. EIS was also used to investigate the effect of fly ash (FA) on the hydration behavior of MOSC. Mercury intrusion porosimetry (MIP), backscattered scanning electron microscopy (BSE), and scanning electron microscopy (SEM) were used to study the evolution of the pore structure and micromorphology of MOSC incorporated with FA. The results show that the resistance values ($R_1$) in the equivalent circuit for MOSC increase with increasing curing time. The incorporation of FA can affect the resistance values for each element in the equivalent circuit. In the early stages of hydration (1 day and 2 days), high-volume FA can reduce the degree of hydration of MOSC paste. At the later stages of hydration, the resistance values ($R_1$) increase with increasing FA content. The MIP, BSE, and SEM results also show that the porosity of MOSC decreases with increasing FA content; the incorporation of FA can significantly improve the morphology of MOSC, resulting in a denser microstructure. This study shows that the electrochemical impedance spectroscopy is a powerful technique to investigate the hydration behavior and process of MOSC, and the results also indicate that FA is a good mineral admixture used as a partial substitute for MOSC cementitious materials.

For geotechnical construction and maintenance, assessing the shearing behavior at the soil–structure interface is significant. This study presents an experimental investigation into the effect of the grain size distribution of a sandy soil on the shearing behaviors at the soil–structure interface, using a modified direct shear apparatus. Five soil samples with different coefficients of uniformity were prepared. The normalized roughness of the structure surface (the ratio between the maximum roughness of the structure plate and the mean grain size of the soil); relative density; and maximum, mean, and minimum grain sizes of all samples were controlled in the same way. During the tests, the shear force, shear displacement, and vertical displacement were monitored. The results show that at a given shear displacement and normal stress, the sample with lower coefficient of uniformity $C_u$ presented higher shear stress and more pronounced dilative behavior. The increase of $C_u$ led to a decrease of the friction angle for the soil–structure interface (at both peak and ultimate states) and a decrease of the maximum vertical deformation of the soil sample during the shearing process. As $C_u$ increased, the main force chain at the soil–structure interface turned from contact between the coarser grains to that mainly formed by the finer grains, resulting in a decrease of the shearing resistance. In comparison with the previous relevant studies, the decreasing trend of the friction angle with the increase of $C_u$ is strongly supported.

Many studies and experiments have investigated the effective parameters, mechanisms, and methods of preventing moisture damage to asphalt mixtures. These experiments presented only a numerical index, in which the performance of asphalt mixture against moisture. Due to the lack of relationship between the damage mechanism in the laboratory and the field conditions, measurement of the material properties and their role, and corrective solution, it seems necessary to present more appropriate methods based on the characteristics of the asphalt mixture which are determinative in the occurrence of moisture damage. This study provides a model for prediction of moisture susceptibility of asphalt mixtures using thermodynamic parameters and mixing design properties. Twenty-four combinations of asphalt mixtures were investigated using three types of aggregates and additives and two types of base bitumen. The components of surface free energy (SFE) for bitumen and aggregate were measured using the sessile drop (SD) method and the universal sorption device (USD), respectively. The modified Lottman test method was used to predict the field performance of asphalt mixtures resistance to moisture damage. The results obtained from the prediction show that the SFE of cohesion (CE), the SFE of bitumen–aggregate adhesion (AE), the specific surface area of aggregates (SSA), and apparent asphalt film thickness (AFT) parameters directly affect the resistance to moisture damage, whereas the energy released by the system during stripping [debonding energy (DE)] and the permeability of asphalt mixtures (PA) inversely affect the strength. DE and SSA had the greatest effect on decreasing and increasing the strength of asphalt mixture against moisture, respectively.

This study evaluated ornamental stone fines (OSF) and steel slag fines (SSF) as potential fillers for asphalt mixtures. The fine aggregate matrix (FAM) phase was chosen for performance tests. Four different types of FAM were produced, changing the type of filler among them. The effects of those materials on the FAM were investigated by performing dynamic frequency sweep tests to evaluate linear viscoelastic stiffness characteristics through the analysis of dynamic shear modulus master curve, and semicircular bending and time sweep tests to evaluate fracture characteristics through the analysis of fracture energy and damage characteristics based on the simplified viscoelastic continuum damage model, respectively. The results indicate that the FAM with a blend of OSF and SSF has better overall performance than the other studied FAMs, possibly due to its intermediate stiffening effect and higher resistance to fracture. It is also implied that the OSF and SSF by-products could be used as asphalt concrete filler, which can bring potentially significant environmental-economical benefits to countries such as Brazil, where those materials usually have been disposed.

Consumption of resources is increasing as the world’s population and industrialization rise, so that natural resources are being exhausted. Therefore, the use of waste and recycled materials is very important to achieve environmental and economic benefits. This study assessed the effects of compaction energy and the role of a binder on the properties of two control groups (A and B) of hot-mix asphalt used for surface layers, prepared according to European Standards. Group A consisted of stone dust, subfractional glass, and a binder. Group B comprised stone dust, subfractional stone aggregate, and a binder. Laboratory testing determined the effect of the observed variables on the density of asphalt samples and ratio of air voids and voids filled with bitumen. The findings indicate that the compaction energy and glass fraction in the asphalt mixture had a significant influence.

Some culverts and pipes installed under roadways several decades ago are reaching the end of their service life. The excavation and replacement of these buried structures will cause disruption to their service and require significant funding. Trenchless methods (e.g., sliplining) have been increasingly used to rehabilitate deteriorated buried structures (e.g., corroded steel pipes). Sliplining involves the placement of a new pipe liner inside an existing deteriorated pipe and the grouting of the space between the liner and the existing pipe. In this experimental study, parallel-plate loading tests were carried out to evaluate the effect of sliplining on the behavior of corrugated steel pipes with different degrees of corrosion. The nominal diameters of the corrugated steel pipes and polyvinyl chloride liner were 305 and 254 mm, respectively. This study investigated three different degrees of simulated corrosion of the steel pipes (0%, 50%, and 90%). The corrosion in each steel pipe was simulated by cutting out some steel segments along the invert of the pipe. A low-strength, normal-density grout was used to fill the space between the steel pipe and the liner. The pipes without and with sliplining were tested for their load-carrying capacity, stiffness, vertical and horizontal diameter changes, and average strains and curvatures. The experimental results show that prior to sliplining, the steel pipe with a 90% cutout behaved in a stiffer manner than that with a 50% cutout at a higher applied load. After sliplining, however, the steel pipe with 50% corrosion behaved in a stiffer manner than the pipe with a 90% cutout. Sliplining increased the load-carrying capacity and stiffness of the pipe. The location of the liner relative to the existing pipe had a minor effect on the behavior of the sliplined steel pipe.

As a by-product of petroleum, asphalt reserves have dwindled with the exhaustion of petroleum resources. Therefore, it is necessary to seek alternative asphalt binders to reduce asphalt consumption without sacrificing the pavement properties of asphalt mixtures. At present, bioasphalt modification technology has been widely studied to partly replace asphalt binders. However, balancing performance and economy is more difficult with modified bioasphalt binders than with typical modified asphalt binders [e.g., 5% styrene-butadiene-styrene (SBS)–modified asphalt binder]. Hence, a new modification technology using bio-oil, nanomaterials, and polymers was developed in this study. The optimal modification formulas of the composite modifiers are determined via the orthogonal experimental design method. The pavement properties (high-temperature performance, low-temperature performance, antiaging performance, and water stability performance) of the proposed modified bioasphalt binders and their mixtures were tested against those of the 5% SBS-modified asphalt binder and AH-70 base asphalt binder, and the results showed that the proposed modified bioasphalt binders exhibited satisfactory pavement properties. An economic analysis showed that the costs of the proposed modified bioasphalt binders are lower than those of the 5% SBS-modified asphalt binder.

Subgrade and foundation soils undergo freeze and thaw cycles in seasonally frozen regions that leads to changes in its mechanical properties, causing the degradation of its service performance. This study aims to investigate the effects of freeze–thaw cycles on the dynamic mechanical properties of compacted silty clay. Specifically, the effects of number of freeze–thaw cycle, confining pressure, initial compaction degree, and initial water content on the dynamic shear modulus and damping ratio were studied by using resonant column tests. The test results showed that both maximum dynamic shear modulus and maximum damping ratio of the compacted silty clay sample had a decreasing trend with the increasing number of freeze–thaw cycles. In addition, the maximum dynamic shear modulus was significantly increased with the initial compaction degree and it was decreased with the initial water content, while the maximum damping ratio was decreased with the initial compaction degree and it was increased with the initial water content. Finally, the empirical models of maximum dynamic shear modulus and maximum damping ratio were proposed to consider the varied parameters.

In this study, incinerated sewage sludge ash (ISSA) was applied to replace ordinary portland cement (OPC) and quick (unhydrated) lime at different ratios of 0%, 20%, and 50% for improving the properties of marine sediments with high water content by solidification/stabilization (S/S) method. Then, the effects of different binders and curing time (7 and 28 days) on sediment properties, including unconfined compressive strength (UCS), shear strength, durability, and leachability of metals were investigated. Test results indicated that lime–ISSA binder had several advantages over OPC–ISSA binder owing to its lower cost, lower environmental footprints, and better strength gains. The UCS, deformation resistance, and shear strength of the specimens prepared using lime as the binder were improved with the increasing addition of ISSA, and the water permeability was also effectively reduced. The results of environmental impact assessment (in particular leaching characteristics) indicated that the leachability of heavy metals in the lime–ISSA stabilized sediments was effectively mitigated. The proposed fill material complied with the acceptance criteria for engineering fills applications. A series of spectroscopic/microscopic laboratory tests including mercury intrusion porosimetry (MIP), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were performed to investigate the mechanisms controlling strength development and metals immobilization. The chemical reactions between the sediments, ISSA, and lime resulted in the formation of hydrated cementitious compounds that facilitated the decrease in pore volume and increase in strength and stabilization of heavy metals. On the whole, the lime–ISSA system could replace the OPC–ISSA binder to particularly improve the geotechnical and environmental properties of the contaminated sediments.

Aggregates, as main components of asphalt mixtures, have a great influence on the road performance of mixtures. Similar to biological genes determining biological traits, the macroscopic performances of aggregates are determined by the aggregates’ properties. Specifically, the crushing process determines morphological characteristics of aggregates, and the chemical composition determines the physical and mechanical properties. In order to predict aggregates’ properties and rationally select aggregates, the effect of chemical composition on the properties of coarse aggregates was investigated in this paper. The physical and mechanical properties of different aggregates were tested, including the apparent relative density, water absorption, crushing value, and Los Angeles wear value. The chemical composition was measured by X-ray fluorescence (XRF). Moreover, the Pearson correlation of chemical compositions and physical and mechanical properties of coarse aggregates was analyzed by Statistic Package for Social Science (SPSS) software, and results showed that ${\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{SiO}}_2$ can improve the properties of coarse aggregates, whereas CaO had a negative effect on aggregate performance. Therefore, aggregates with higher ${\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{SiO}}_2$ content can be selected for pavements with high strength requirements.

Masonry walls resist both in-plane and out-of-plane forces through the bond between the brick unit and mortar. Moisture content or saturation level of the brick unit at the time of construction is one of the key contributing factors in bond strength. Absorption of water from mortar by brick alters the development of a mechanical key that establishes the bond strength. In this study, the effect of the moisture content of bricks, at the time of construction, on shear and tensile bond strength is investigated for fired clay and fly ash bricks. The results of this study indicate that around a 75% saturation level of the brick unit yields the highest values of shear and tensile bond strength of clay and fly ash brick masonry with cement mortar. Adequate prewetting of brick units at the time of construction will ensure the desired moisture content and subsequently help to achieve a good bond strength.

Waste from soda–lime glass is a solid waste usually available near urban centers. This study examines the potential use of such a material as a construction component. Finely ground waste glass mixed with carbide lime might be able to act as a hydraulic cement and could be shaped into blocks and used as an alternative to masonry blocks or bricks. It also could be applied in stabilized rammed wall construction, as well as in beds of pipelines and spread footings. When in alkaline environments, pozzolanic reactions occur between silicates in amorphous phases (present in ground waste glass) and ${\mathrm{Ca}}^{2+}$ (found in lime). This technical note establishes the effects of carbide lime content and dry density on the properties (i.e., strength and stiffness) of compacted ground waste glass–carbide lime mixes. More specifically, it quantifies the unconfined compressive strength ($q_u$) and the shear modulus at small strains ($G_0$) of ground waste glass mixed with carbide lime as a function of the porosity/lime index. Results show that $q_u$ varies from about 2.1 to 4.7 MPa and $G_0$ from about 3,600 to 8,500 MPa, depending on curing time, porosity, and amount of carbide lime. Tobermorite, a calcium silicate hydrate mineral, was detected as the key crystalline phase shaped by the cured ground glass–carbide lime blends after 28 days of curing.